Method and communication apparatus for controlling a jitter buffer

a communication apparatus and buffer technology, applied in multiplex communication, data switching networks, instruments, etc., can solve problems such as buffer overflow, receiving nodes will eventually experience buffer underflow, and cannot be locked

Inactive Publication Date: 2008-11-11
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This approach improves speech quality by reducing buffering delay in jitter buffers, preventing overflow and underflow, and maintaining acceptable audio quality even under severe clock skew conditions.

Problems solved by technology

One problem associated with IP-telephony communication systems, is that individual speech packets in a stream of speech packets generated and transmitted from an originating node to a receiving node in the communication system, experiences stochastic transmission delays, which may even cause speech packets to arrive at the receiving node in a different order than they were transmitted from the originating node.
Another problem that is present in “IP-telephony” as opposed to traditional circuit switched telephony is that the clock that controls sampling frequency, and thereby the rate at which speech packets are produced by the originating node, is not locked to, or synchronized with, the clock controlling the sample playout rate at the receiving node.
In an “IP-telephony” call involving two personal computers (PC), it is typically the sound board clocks of the PCs that control the respective sampling rates which is known to cause problems.
If the clock at the originating node is faster than the clock at the receiving node, the delay in the jitter buffer will increase and eventually cause buffer overflow, while if the clock at the originating node is slower than the clock at the receiving node, the receiving node will eventually experience buffer underflow.
In this case, a crude correction will create perceptually unacceptable artefacts.

Method used

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  • Method and communication apparatus for controlling a jitter buffer

Examples

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Embodiment Construction

[0020]FIG. 1 illustrates an exemplary communication system SYS1 in which the present technology is applied. The communication system SYS1 comprises a fixed terminal TE1, e.g. a personal computer, a packet switched network NET1, which typically is implemented as an internet or intranet comprising a number of subnetworks, and a mobile station MS1. The packet switched network NET provides packet switched communication of both speech and other user data and includes a base station BS1 capable of communicating with mobile stations, including the mobile station MS1. Communications between the base station BS1 and mobile stations occur on radio channels according to the applicable air interface specifications. In the exemplary communication system SYS1, the air interface specifications provides radio channels for packet switched communication of data over the air interface. However for transport of speech over the air interface, radio channels are provided which are basically circuit switc...

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Abstract

A method for controlling a jitter buffer and a communication apparatus implementing the method and functioning as a first node of a communication system, wherein the jitter butter is adapted to buffer a stream of blocks of compressed speech information generated in a second node in the communication system, transmitted to and received in the first node. Blocks of compressed speech information in said stream of blocks are selected (201) according to a predetermined rule based on the current buffering delay of the jitter buffer and at least one characteristic of said blocks of compressed speech information. Predetermined actions aiming at reducing buffering delay in the jitter butter are applied (202) to the selected blocks.

Description

[0001]This application is the U.S. National phase of international application PCT / SEO1 / 02798 filed 14 Dec. 2001 which designates the U.S.TECHNICAL FIELD OF THE INVENTION[0002]The invention relates to a method for controlling a jitter buffer in a node of a communication system and a communication apparatus implementing said method in a communication systemDESCRIPTION OF RELATED ART[0003]Currently, there is a strong trend in the telecommunication business to merge data and voice traffic into one network using packet switched transmission technology. This trend, often referred to as “Voice over IP” or “IP-telephony”, is now also moving into the world of cellular radio communications.[0004]One problem associated with IP-telephony communication systems, is that individual speech packets in a stream of speech packets generated and transmitted from an originating node to a receiving node in the communication system, experiences stochastic transmission delays, which may even cause speech p...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): H04L12/28H04J3/06G06F5/00H04LH04L47/2416H04L47/32
CPCH04L47/10H04L47/14H04L47/2416H04L47/283H04L47/32H04L49/90H04W28/14H04W8/04
InventorSUNDQVIST, JIMJANSSON, FREDRIK
OwnerTELEFON AB LM ERICSSON (PUBL)